The spine can be considered to be a series of movable segments made up of vertebrae and discs. Due to trauma, disease, and/or aging, the spine may be subject to degeneration. This degeneration may destabilize the spine and cause pain and/or nerve damage. Medical procedures are often required to either ease back pain, repair damage, or to prevent future damage.
One procedure that is often used to treat back or neck pain or other spinal damage is spinal fusion. Spinal fusion is a surgical technique used to combine two or more adjacent vertebrae. Supplemental bone tissue or a synthetic substitute is used in conjunction with the patient's natural osteoblastic processes in a spinal fusion procedure. Spinal fusion is used primarily to eliminate back pain caused by the motion of the damaged vertebrae by immobilizing the damaged vertebra through fusion with the adjacent vertebrae. Conditions for which spinal fusion might be done include degenerative disc disease, treatment of a spinal tumor, a vertebral fracture, scoliosis, degeneration of the disc, spondylolisthesis, or any other condition that causes instability of the spine.
One problem with typical prior art fusion techniques is that fusion devices, or associated plates or fasteners, may protrude from the spine, or work themselves loose and back out of or away from the bone causing discomfort, damage, soft tissue erosion or danger to surrounding vascular or neurological tissues. Another problem with spinal fusion techniques relates to device migration or subsidence. For example, prior to formation of a bone fusion, a vertebral endplate may fracture, or an underlying or pre-existing Schmorls Node may result in a weakened vertebral body causing device migration from the desired position or collapse of the intended fusion space. In examples where bone screws are used, inadequate fixation of the bone screws into the vertebral bodies may allow device migration as the bone resorbs or remodels. In yet another example, poor selection or preparation of bone tissue or a synthetic bone substitute used to fill the inner body space of the interbody fusion device results in a poor, weak or non-fusion. Still other issues such as poor endplate preparation and unstable surfaces; failure of the surgeon to provide adequate blood flow or blood transfer to the graft site via endplate perforation, may result in a failure to fuse bone. Yet other problems associated with poor surgical technique; anatomic obstructions, such as bony structures, delicate arterial structures or other soft tissues; inadequate instrumentation or a combination of these may contribute to a poor outcome.
There is therefore a need for spinal fusion devices and related spinal fusion procedures that adequately addresses degenerative disc disease and other spinal conditions, while providing improvements over the prior art.